中文摘要：

春季冻土融化导致黄土地区边坡冻融灾害频繁发生,因对其机理性研究的不足,目前对此尚不能进行量化分析和预测。本文首先对西安Q3原状黄土进行室内冻融试验,研究冻融作用对其剪切强度的影响;其次,基于室内试验数据,运用有限元强度折减法对黄土边坡冻融失稳特征进行数值计算分析。研究发现：黄土试样粘聚力随冻融次数增加呈指数衰减趋势;粘聚力随含水率增加表现出线性衰减特征且冻融后粘聚力与含水率的变化曲线近似重合;内摩擦角无明显规律性变化。黄土边坡安全系数随冻融次数增加亦呈指数衰减趋势,这与粘聚力随冻融次数的变化规律是一致的;安全系数随冻融深度和冻融区初始含水率增加显著减小且降低幅度逐渐增加;安全系数随坡度系数和放坡级数增加近似呈线性增加特征。黄土边坡冻融滑裂面与季节冻融深度线近似重合。

英文摘要：

The thawing of frozen soils in spring has caused the frequent freezing-thawing disaster for slope in loess regions. Moreover,the disaster can＇t be quantitatively analyzed and predicted,which is induced by the weak mechanism research. Based on that,the paper firstly carried out freeze-thaw test to study the influence of freeze-thaw action on the shear strength of xi＇an Q3 undisturbed loess. The results show that the cohesion of loess exponentially decreases with freezing and thawing times increasing. With the increase of water content,the cohesion linearly decreases,and has a approximately same variation after freezing and thawing. The internal friction angle has no obvious variation during the whole freezing-thawing process. The safety factor of loess slope also exponentially decreases with freezing and thawing times increasing,which is corresponding with the relationship between the cohesion and freezing-thawing times. With the increase of the freezing-thawing depth and water content in active layer,the safety factor decreases with a growing gradient. The safety factor linearly increases with the increase of slope coefficient and sloping steps. The freeze-thaw slip surface of the loess slope is approximately consistent with the seasonal freeze-thaw depth line.